1. Field of the Invention
This invention relates generally to installation of clutch assemblies in automatic transmissions, and more particularly, but not by way of limitation, to apparatus and methods for the installation of clutch assemblies in General Motors Type 400 and Type 350 Turbo Hydra-Matic transmissions.
2. Description of the Prior Art
Automatic transmissions typically used in modern automobiles generally include several clutch assemblies which are interconnected with each other by means of splined connections. The clutch assemblies are actuated in various combinations in order to produce the desired output motion from the transmission.
Each clutch assembly typically includes a clutch casing having a cylindrical cavity therein. In that cavity there is located a stack of annular clutch plates. The stack of clutch plates is comprised of alternating steel plates and friction plates. The steel plates have a plurality of radial outer teeth which engage or mesh with radially inner axial splines of the clutch casing. The friction plates have a plurality of radially inner teeth for engagement with an externally axial splined cylindrical body of another clutch assembly or of another part of the transmission to which power must be transmitted. Also, disposed in the cylindrical cavity of the clutch casing is an annular piston which acts to exert an axial compressive force on the stack of clutch plates when fluid under pressure is supplied to the piston.
This invention concerns the difficulty which has long been experienced in inserting the externally splined cylindrical body into engagement with the radially inner teeth of the friction plates of the clutch assembly. Preferably, in order to slip the cylindrical body smoothly into engagement with one single axial motion, the teeth of the several friction plates must be axially aligned so as to fit between the axial splines of the cylindrical body.
Unfortunately, this is very difficult to accomplish with the methods of the prior art. The methods of assembly of the prior art require that the cylindrical body be inserted into engagement with the friction plates while those friction plates are free to rotate relative to one another. This is because there has previously been no means for supplying an axial compressive force to the clutch plates while the cylindrical body was being inserted, so as to keep the inner teeth of the clutch plates in axial alignment.
This problem is compounded when inserting the cylindrical body into a clutch assembly which is already installed in a transmission housing, because the cylindrical body typically includes other structures which make it impossible to see the clutch plates as the cylindrical body is being inserted. This requires that the assembly be made by feel, and typically involves the jiggling back and forth of the cylindrical body with a reversing radial motion so that the cylindrical body is gradually worked into the stack of clutch plates by engaging the splines of the body successively with the radially inner teeth of one friction plate, then the next friction plate and so on.
This problem is of particular significance on the assembly lines of automotive construction plants where great numbers of these clutch assemblies are installed daily.
The methods and apparatus of the present invention overcome the difficulties described above in the installation of clutch assemblies within automatic transmissions. This is done by the use of a cylindrical alignment tool and a means for supplying fluid under pressure to the piston of the clutch assembly. It is estimated that these tools can typically reduce assembly time of a transmission by one hour.
The alignment tool is a cylindrical alignment tool having a plurality of axial splines constructed for engagement with the radially inner teeth of the friction plates of the clutch assembly. The cylindrical alignment tool and the clutch plates are installed within the clutch housing. This may either by done by first positioning the alignment tool and then placing the clutch plates about the alignment tool, or the clutch plates may first be stacked within the clutch housing and then the alignment tool may be inserted therein. It will be noted, however, that the installation of the alignment tool within a stack of clutch plates is much easier than the installation of a typical cylindrical body that must be installed in the transmission, because the alignment tool is relatively small and lightweight and there is no obstructing structure which prevents visual observation of the alignment tool as it is being inserted in the clutch plates.
After the alignment tool and clutch plates are installed within the clutch casing, a high pressure fluid is directed to the piston of the clutch assembly so that the piston applies an axial compressive force on the clutch assembly to retain the radially inner teeth of the friction plates in axial alignment. Then the cylindrical alignment tool is removed from the clutch assembly while the high pressure fluid is still being supplied to the piston. The piston retains the radially inner teeth of the friction plate in axial alignment even after the alignment tool is removed.
Then, the cylindrical body of the next clutch assembly, or the next component of the transmission which must engage the first clutch assembly, is inserted within the stack of clutch plates with a single axial sliding motion. This is possible because the radially inner teeth of the friction plates are held in axial alignment by the high pressure fluid directed to the piston of the clutch assembly.